Several species of bacteria are able to secrete exopolysaccharides or alginates that are essential for virulence as the exudate provides a mechanism for adherence and colonization. One particularly important example of such bacteria is Pseudomonas aeruginosa, a common soil bacterium which inhabits individuals generally, but is particularly destructive in subjects with cystic fibrosis. Cystic fibrosis is an autosomal recessive genetic disorder linked to dysfunctional CFTR chloride channels on cell surfaces. It is characterized by production of thick mucus which prevents clearance of bacteria, resulting in chronic infection and inflammation. Because P. aeruginosa produces biofilm in the lungs and digestive systems of these subjects, and the subjects are unable to clear this biofilm, P. aeruginosa infection is a major cause of death among such individuals.
Many bacteria exhibit mucoid (resembling mucus) phenotype as a response to their growth environment. The mucoidy is generated by bacterial production of extracellular polysaccharides (exopolysaccharide or EPS). Various EPS molecules that include frucose, rugose and glucose residues have been characterized. Examples of bacteria producing mucoid phenotype include alginate producing Pseudomonas and Azotobacter species (i.e., P. aeruginosa, Azotobacter vinelandii), rugose producing Vibrio species (i.e., Vibrio cholerae), xanthan producing Xanthomonas species (i.e., Xanthomonas campestris), gellan producing Sphingomonas species (i.e., S. paucimobilis), curdlan-type EPS producing Cellulomonas, Alcaligenes and Agrobacterium species (i.e., Cellulomonas flavigena, Alcalifenes faecalis) and Shewanella, Bordetella and Streptococcus species producing various uncharacterized EPS, among others. In fact, under unfavorable growth conditions, many bacteria can switch to a mucoid phenotype to resist the environmental stress and adapt to unfavored conditions. Biofilms represent a typical structured adaptation environment in which many bacteria co-exist and secrete extracellular polysaccharides which aid them to stick to surfaces for growth and colonization, provide a protective barrier around them and adapt to their environment in a microbial community. The exopolysaccharides produced by mucoid Pseudomonas that occupy the lungs of cystic fibrosis patients are generally alginates which are O-glycosyl linked D-mannuronate and L-guluronate residues.
It is understood that, in order to produce these biofilms, the essential components required must be made available by the metabolic system of the bacterium. The present invention provides means to disrupt this ability by disabling an essential step in this metabolic sequence.